Chloroidium antarcticum Darienko, Lukešová & Pröschold, 2018

Darienko, Tatyana, Lukešová, Alena & Pröschold, Thomas, 2018, The polyphasic approach revealed new species of Chloroidium (Trebouxiophyceae, Chlorophyta), Phytotaxa 372 (1), pp. 51-66 : 60-62

Chloroidium antarcticum Darienko, Lukešová & Pröschold sp. nov.

Diagnosis: Young cells are ellipsoidal, broadly ellipsoidal to almost spherical, 13.6 × 10.9 μm–16.4 × 11.8 μm. Cell wall is relatively thin. Chloroplast is parietal, band-shaped, and deeply lobed. Mature vegetative cells ellipsoidal to broadly ellipsoidal 19.1 × 16.4–24.5 × 20.0 μm. Chloroplast is parietal, deeply lobed, and massive, with one naked pyrenoid. Nucleus is single, large, and is good visible. The cell wall of mature vegetative cells becomes slightly ticker. Cells accumulate some small vacuoles with age, which are located in the center or periphery of the cells and which sometimes slightly remove chloroplasts from the cell wall.

Reproduction determined by equal and unequal size of autospores. Autospores of equal size are produced at 8–64 per sporangium and have a narrowly ellipsoidal shape. Autosporangia of this type are 21.8 × 20.0 to 26.8 × 20.9 μm in size. Autospores in sporangia approximately 10.0 × 4.5 μm in size.

Autospores of unequal size were produced at a rate of 4–16 per sporangium. According to the cell shape and the size of autospores, they can by classified into three types. (i) autosporangia containing 4–8 spores, which contain large and small autospores of the same broadly ellipsoidal cell-shape. Large autospores are 15.5 × 13.5 μm in size, while small autospores are approximately 7.0 μm in size. (ii) Sporangia with 4–16 daughter cells, containing one large broadly ellipsoidal cell and other small narrowly ellipsoidal cells. Large autospores are 13.6 × 10.9–15.5 × 13.5 μm, and small are approximately 9.1 × 5.0 μm. (iii) Sporangia with 4 spores containing two large and two small broadly ellipsoidal spores. Large autospores are 10.9 × 8.2–13.6 × 10.9 μm in size, and small are approximately 6.4–5.0 μm in size.

The liberation of autospores is achieved by apical rupturing of sporangia. The remains of sporangial cell wall are usually bag-shaped. The liberation of autospores continues for a long time after rupturing. Often, one autospore remains in the sporangial cell wall and develops into a mature vegetative cell.

Differs from other Chloroidium species by its larger cell size, different types of autosporangia and CBCs in its ITS-2.

Type locality: soil, South Shetlands, King George Island, Ecology Glacier, Antarctica.

Holotype (designated here): The strain ISBAL-1013 is cryopreserved in a metabolically inactive state at the SAG, Göttingen , Germany.

Iconotype (in support of the holotype designated here): Fig. 6A–G in this study.

Figures

FIGURE 6. Morphology and phenotypic plasticity of the new Chloroidium species. A.–G. C. antarcticum; H.–M. C. viscosum; N.–V. C. arboriculum; scale bar = 10 μm.